1.Polling methodology is circular. Since a pollster will only sample a tiny fraction of the electorate, he must guess at what constitutes a representative sample group. So the output corresponds to the input. If you oversample Democrats and undersample Republicans, the polling results will mirror the sample group—which may or may not correspond to the distribution of the actual turnout. The sampling self-selects for the results.

Indeed, pollsters will even adjust the numbers to “correct” for the results if they think the results are unrepresentative.

2.The “Bradley effect.” It’s possible that some respondents lie to pollsters because they’re sensitive to the charge of “racism.”

Whether there is a “Bradley effect” is debatable. And whether it’s in play this time around is inherently unpredictable.

3.While McCain doesn’t have the number of paid boots on the ground that Obama has, he may have a lot of invisible boots on the ground. By tapping Palin, he was potentially tapping into an informal network of homeschooling moms and other suchlike. That doesn’t show up on the radar screen. Indeed, values voters are generally invisible to the liberal media because the liberal media takes no interest in this demographic niche.

4.While McCain’s position on amnesty is anathema to many conservatives, it may play better to the Latino voting block in a key state like Florida. That, too, remains to be seen.

5.Younger voters favor Obama, but historically, they don’t turn out in droves. Whether this year is an exception remains to be seen.